1. Field of the Invention
The present invention relates to an ink ejection device for ejecting ink droplets from orifices in a printing head. More particularly, the invention relates to an ink ejection device wherein printing can be properly continued when an amount of ink remaining in an ink reservoir is small.
2. Description of the Related Art
There has been known an ink ejection device with a means for determining when the level of ink in an ink cartridge, or other type of ink reservoir for supplying ink to the printing head, has run low. When the amount of ink is determined to have run low, a warning to that effect is displayed on a display unit or a buzzer is sounded to bring the low level to the user's attention. The user then replenishes the supply of ink by changing the ink cartridge, refilling the ink reservoir, or other method. When no ink or ink cartridge is available, the user must go to a store, buy ink or an ink cartridge, and then replace the ink before continuing to print.
Because the low ink level is announced by a display or warning buzzer, a user has no way of knowing that the level of ink is low unless he or she happens to be near the ink ejection device. Even if a user notices the buzzer or display, he or she may ignore it and continue printing without replenishing the ink supply. As a result, printing sheets may be outputted half printed with an image and half blank when the ink runs out totally. Also, air can enter the head when ink totally runs out, damaging the head.
These kinds of problems can occur when the ink ejection devices are used in printers or word processors. However, the problems become even more serious when the ink ejection device is used for a facsimile machine. Sometimes facsimile messages are received in the middle of the night or other time when no operator is present. Under such circumstances, it is impossible for a user to hear or see warnings about a low ink level. Also operators of remote facsimile machines have no way of knowing if the ink level is low and so will attempt to transmit messages. When the facsimile machine attempts to record the received facsimile message when ink is in short supply, sheets may be outputted half blank so that the facsimile message can not be understood. One method of preventing this problem is to store in a memory the portion of incoming messages that can not be printed because of low ink level. However, this solution requires addition of a large capacity reception memory, which would increase costs of producing the device.